Avoid leaking null to __dict__ when unbinding except var

Author: msimacek

graalpython/com.oracle.graal.python.test/src/tests/test_exception.py

@@ -634,3 +634,11 @@ class A: pass
         except UnicodeEncodeError as e:
             errMsg = str(e)
         assert len(errMsg) > 0
+
+    def test_exception_scope(self):
+        g = {}
+        exec("try:1\nexcept Exception as e: pass", g)
+        assert 'e' not in g
+        exec("try:1/0\nexcept Exception as e: pass", g)
+        assert 'e' not in g
+

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/statement/ExceptNode.java

@@ -64,20 +64,23 @@
 public class ExceptNode extends PNodeWithContext implements InstrumentableNode {
     @Child private StatementNode body;
     @Child private WriteNode exceptName;
+    @Child private StatementNode exceptNameDelete;
     @Child private ExpressionNode exceptType;
 
     @Child private ExceptMatchNode matchNode;
 
-    public ExceptNode(StatementNode body, ExpressionNode exceptType, WriteNode exceptName) {
+    public ExceptNode(StatementNode body, ExpressionNode exceptType, WriteNode exceptName, StatementNode exceptNameDelete) {
         this.body = body;
         this.exceptName = exceptName;
         this.exceptType = exceptType;
+        this.exceptNameDelete = exceptNameDelete;
     }
 
     public ExceptNode(ExceptNode original) {
         this.body = original.body;
         this.exceptName = original.exceptName;
         this.exceptType = original.exceptType;
+        this.exceptNameDelete = original.exceptNameDelete;
     }
 
     public void executeExcept(VirtualFrame frame, Throwable e) {
@@ -90,7 +93,7 @@ public void executeExcept(VirtualFrame frame, Throwable e) {
         }
         body.executeVoid(frame);
         if (exceptName != null) {
-            exceptName.executeObject(frame, null);
+            exceptNameDelete.executeVoid(frame);
         }
         throw ExceptionHandledException.INSTANCE;
     }

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/parser/sst/FactorySSTVisitor.java

@@ -711,6 +711,17 @@ private void delTarget(List<StatementNode> blockList, PNode target) {
         }
     }
 
+    protected StatementNode unbindVariable(ReadNode target) {
+        if (target instanceof ReadLocalNode) {
+            return ((ReadLocalNode) target).makeDeleteNode();
+        } else if (target instanceof ReadGlobalOrBuiltinNode) {
+            return DeleteGlobalNode.create(((ReadGlobalOrBuiltinNode) target).getAttributeId());
+        } else if (target instanceof ReadNameNode) {
+            return DeleteNameNode.create(((ReadNameNode) target).getAttributeId());
+        }
+        throw new IllegalStateException("invalid target for unbind");
+    }
+
     @Override
     public PNode visit(ExceptSSTNode node) {
         // we shouldn't visit this node. It should be processed in try
@@ -1253,8 +1264,14 @@ public PNode visit(TrySSTNode node) {
             }
             ExpressionNode exceptTest = exceptNode.test != null ? (ExpressionNode) exceptNode.test.accept(this) : null;
             StatementNode exceptBody = (StatementNode) exceptNode.body.accept(this);
-            WriteNode exceptName = exceptNode.asName != null ? (WriteNode) scopeEnvironment.findVariable(exceptNode.asName).makeWriteNode(null) : null;
-            exceptNodes[i] = new ExceptNode(exceptBody, exceptTest, exceptName);
+            WriteNode exceptName = null;
+            StatementNode exceptNameDelete = null;
+            if (exceptNode.asName != null) {
+                ReadNode readAsNode = scopeEnvironment.findVariable(exceptNode.asName);
+                exceptName = (WriteNode) readAsNode.makeWriteNode(null);
+                exceptNameDelete = unbindVariable(readAsNode);
+            }
+            exceptNodes[i] = new ExceptNode(exceptBody, exceptTest, exceptName, exceptNameDelete);
         }
         PNode result = new TryFinallyNode(new TryExceptNode(body, exceptNodes, elseStatement), finalyStatement);
         result.assignSourceSection(createSourceSection(node.startOffset, node.endOffset));

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/parser/sst/GeneratorFactorySSTVisitor.java

@@ -351,8 +351,14 @@ public PNode visit(TrySSTNode node) {
             ExceptSSTNode exceptNode = node.exceptNodes[i];
             ExpressionNode exceptTest = exceptNode.test != null ? (ExpressionNode) exceptNode.test.accept(this) : null;
             StatementNode exceptBody = (StatementNode) exceptNode.body.accept(this);
-            WriteNode exceptName = exceptNode.asName != null ? (WriteNode) scopeEnvironment.findVariable(exceptNode.asName).makeWriteNode(null) : null;
-            exceptNodes[i] = new ExceptNode(exceptBody, exceptTest, exceptName);
+            WriteNode exceptName = null;
+            StatementNode exceptNameDelete = null;
+            if (exceptNode.asName != null) {
+                ReadNode readAsNode = scopeEnvironment.findVariable(exceptNode.asName);
+                exceptName = (WriteNode) readAsNode.makeWriteNode(null);
+                exceptNameDelete = unbindVariable(readAsNode);
+            }
+            exceptNodes[i] = new ExceptNode(exceptBody, exceptTest, exceptName, exceptNameDelete);
         }
 
         StatementNode result;